Method of making strips or tape from small metal particles

ABSTRACT

Strips or tapes are made in that metal particles are pressed into a porous ingot, a tube is extruded from the ingot, and the tube is flattened and rolled.

finite States Patent [191 Wessel 451 May 22, 1973 [54] METHOD OF MAKING STRIPS OR TAPE FROM SMALL METAL PARTICLES [75] Inventor: Otto Wessel,Duisburg-Ungelsheim,

Germany [73] Assignee: Mannesmann Aktiengesellschaft,

Dusseldorf, Germany [22] Filed: Nov. 23, 1970 [21] Appl. No.: 92,277

[30] Foreign Application Priority Data [56] References Cited UNITED STATES PATENTS 910,684 1/1909 Homer ..72/203 X 2,914,973 12/1959 Crane et al. ..72/208 3,066,403 12/ 1962 Brauchler ....29/420.5

3,189,988 6/1965 Crane ..29/420.5 3,460,235 8/1969 Roberts et a1. ..29/473.3 X 3,489,533 1/1970 Herchenrider et al ..29/420.5 X

FOREIGN PATENTS OR APPLICATIONS 1,124,670 3/1962 Germany .29/420.5

Primary Examiner-Charles W. Lanham Assistant Examiner-V. A. Dipalma Attorney-Smyth, Roston & Pavitt [57] ABSTRACT Strips or tapes are made in that metal particles are pressed into a porous ingot, a tube is extruded from the ingot, and the tube is flattened and rolled.

10 Claims, No Drawings METHOD OF MAKING STRIPS OR TAPE FROM SMALL METAL PARTICLES The invention relates to a method for making strips or tapes out of small, metallic particles, preferably, but not necessarily, steel particles, the particles provided as metal powder, chips, shavings, wire cuttings or the like.

Metal strips are usually manufactured by rolling compact billets or ingot to the desired thickness. Additionally, it is known to make thin, practically nonporous tapes from small metallic particles, such as metal powder or granulated material, also by means of rolling. For this, powder or granulated material is compacted at first by means of two rolls to obtain a porous tape or strip; the material being so processed either when cold or at elevated temperature. Next, the porous strip is alternated between heat treatment and cold rolling, or hot rolling alternates with cold rolling for further compacting of the material. In case of a continuous process for making endless tape or strip, it is necessary to match the strip or tape speed in the several processing stages very accurately. The overall equipment is, thus, rather expensive.

It has been suggested to make strips by means of the same kind of steps, but on an intermittent basis. This requires the strip to be reeled after each step. Intermittent tape making is of advantage particularly in case of processing powder that may react easily with the atmosphere or even with residual oxygen in a protective gas, as the processing area is more easily confined. Nevertheless, the process is still quite cumbersome.

The problem solved by the present invention is to provide a considerably simpler method for making nonporous tapes or strips of limited width and length out of small particles. The raw material processed are small particles in the general sense as outlined above, whereby small is to mean small and light in relation to the final product, e.g., the tape or strip. The particles may have any size and configuration such as metal powder, granulated material, fibers, small and thin wire cuttings, shavings, chips etc. Moreover, the particles used as initial raw material need not be of uniform type, i.e., fine powder, cuttings, shavings, and coarse grain particles may be mixed and processed together.

In accordance with the preferred embodiment of the invention, the particles are at first pressed to obtain a pre-compacted but still porous block or ingot. Next, a tube with solid, e.g., nonporous walls is extruded from the ingot, and finally a flat strip or tape is formed out of the tube. In particular, the tubes wall is flattened, and the flattened wall is rolled down to the desired thickness dimension of the strip or tape to be made.

As to the flattening step, the tube may be pressed flat by means of rolling, whereupon the resulting longitudinal edges are removed, for examples, by means of edging or trimming. This way, two strips are produced, each having width about equal to half the peripheral dimension of the tube. The two strips are then rolled, preferably cold rolled to obtain the desired thin strips or tapes.

In the alternative, the extruded tube can be cut longitudinally, opened up and spread flat. This way, a strip of twice the width is produced. The longitudinal cut can be provided upon the tube as withdrawn from the extrusion mold or press, i.e., while still warm. Alternatively, the cold tube can be sawed or slotted or the like. The tube could also be cut longitudinally in several places. However, in the preferred form of practicing the invention, the extruded tube is cut or slotted in a single cut right behind the press and when still warm; thereafter the cut tube is folded up, i.e. spread, to obtain a flat strip. Also, in this case, the preferred form of finishing the process is by cold rolling the strip as formed from the tube.

The method can be improved by working the extruded tube, for example, by means of pilgering-rolling to obtain a tube of smaller diameter and/or smaller wall thickness. In this case, the final step of making a strip out of the tube needs to operate on thinner material only. The tube wall thinning process is to be carried out prior to flattening of the tubes wall. In particular, tube slotting and spreading or flattening of the unslotted tube will be carried out after the tubes wall has been thinned through pilger rolling or the like.

Another improvement involves heat treating of the pre-compacted ingot for changing, for example, the composition. Also, the ingot could be heated in a protective atmosphere prior to extruding. Ingots that include easily reacting alloy components are preferably clad, by welding a cover or envelope around them.

The extruded tube may have any kind of cross section. For example, it may be rectangular, square shaped, oval, round, partially ring-shaped. However, the preferred mode of practicing the invention is to extrude a tube having completely circular, ring-shaped cross section; this is so as tooling is simpler in this than in other cases. Also, twisting of the tube about its longitudinal axial cannot always be avoided during extrusion. In case of a circular tube, such twisting is not important, particularly as to subsequent processing.

The dimensions of the tube to be extruded depends primarily upon the force available in the extrusion press. Secondary considerations are given to the desired width of the strip to be made. A particular press will produce a particular tube, and a strip of particular width/thickness relation can be made therefrom (e.g. through longitudinal cutting as aforedescribed). Narrower strips are preferably cut from such a strip, wider strips are produced by longitudinally welding strips together prior to rolling.

The following example was practiced with particular advantage.

Clean, coarse saw shavings of austenitic Cr Ni steel is pressed into a porous ingot of 124.5 mm diameter, 200 mm height and a relative density of percent. The ingot was clad in an iron cover by means of welding iron sheets around the ingot, so as to protect the ingot from oxidation. A tube of 60 mm outer diameter and 5 mm wall thickness was extruded from that ingot. The tube was slotted longitudinally, folded up and cleansed in acid or the like. This semi-finished strip was then cold-rolled for a reduced thickness of 0.5 mm. Subsequently, the strip was longitudinally cut to obtain three strips of 60 mm width each. The outer edges were trimmed and the resulting waste" was used for making ingots again.

The method in accordance with the invention is usable for making sheet metal strips or tapes of any kind of material, provided the material can be extruded. The invention is of particular importance for those kinds of materials which can be produced as powder only for reasons of the particular metallurgy involved. For example, mixtures of metal and oxides or other components may well result in powderous products and strip making will be conducted with advantage under utilization of the principles of the present invention. The components permissible must not produce any alloy with the material of the extrusion mold.

The method in accordance with the invention, is very economical as the raw material used is in many cases the waste material from other processes. This is particularly of interest as that waste may include shavings, cuttings etc. of high alloyed steel, i.e., of high quality steel. Also, the method proved to be very economical in case small quantities of narrow strips are to be made having unusual or rarely used consistency such as used for tape electrodes for deposition welding for hard facing etc.

The invention is not limited to the embodiments described above but all changes and modifications thereof not constituting departures from the spirit and scope of the invention are intended to be included.

I claim:

1. Method of making metal strips or tapes, using metal particles such as powder, shavings etc., comprising the steps of:

pressing a quantity of these metal particles to obtain a porous ingot; extruding a nonporous tube from the ingot, the tube having inherently a curved wall configuration; and flattening the curved wall configuration of the tube so as to form at least one strip out of the tube.

2. Method as in claim 1, the strip making, including rolling the flattened wall.

3. Method as in claim 2, the flattening step including flattening the tube as a whole, trimming the edges to obtain two strips.

4. Method as in claim 2, the flattening step being preceded by longitudinally cutting the tube, the flattening step being comprised of spreading the tube wall.

5. Method as in claim 2, the rolling step including cold-rolling the flattened wall.

6. Method as in claim 2, including the step of longitudinally welding the edges of plural flattened strips to obtain a wider strip, and rolling the wider strip.

7. Method as in claim 1, including the step of reducing the wall thickness of the extruded tube prior to strip forming.

8. Method as in claim 1, including the step of pilger rolling the extruded tube.

9. Method as in claim 1, including the step of reducing the diameter of the extruded tube prior to strip forming.

10. Method as in claim 1, including the step of heat treating the ingot prior to extrusion. 

1. Method of making metal strips or tapes, using metal particles such as powder, shavings etc., comprising the steps of: pressing a quantity of these metal particles to obtain a porous ingot; extruding a nonporous tube from the ingot, the tube having inherently a curved wall configuration; and flattening the curved wall configuration of the tube so as to form at least one strip out of the tube.
 2. Method as in claim 1, the strip making, including rolling the flattened wall.
 3. Method as in claim 2, the flattening step including flattening the tube as a whole, trimming the edges to obtain two strips.
 4. Method as in claim 2, the flattening step being preceded by longitudinally cutting the tube, the flattening step being comprised of spreading the tube wall.
 5. Method as in claim 2, the rolling step including cold-rolling the flattened wall.
 6. Method as in claim 2, including the step of longitudinally welding the edges of plural flattened strips to obtain a wider strip, and rolling the wider strip.
 7. Method as in claim 1, including the step of reducing the wall thickness of the extruded tube prior to strip forming.
 8. Method as in claim 1, including the step of pilger rolling the extruded tube.
 9. Method as in claim 1, including the step of reducing the diameter of the extruded tube prior to strip forming.
 10. Method as in claim 1, including the step of heat treating the ingot prior to extrusion. 